In string theory, a paradigm shift could be imminent. In June, a team of string theorists from Harvard and Caltech published a conjecture which sounded revolutionary: String theory is said to be fundamentally incompatible with our current understanding of “dark energy” — but only with “dark energy” can we explain the accelerated expansion of our current universe.

Timm Wrase of the Vienna University of Technology quickly realized something odd about this conjecture: it seemed to be incompatible with the existence of the Higgs particle. His calculations, which he carried out together with theorists from Columbia University in New York and the University of Heidelberg, have now been published in Physical Review. At the moment, there are heated discussions about strings and dark energy all around the world. Wrase hopes that this will lead to new breakthroughs in this line of research.

The theory for everything

Great hope is placed in string theory. It is supposed to explain how gravity is related to quantum physics and how we can understand the laws of nature, which describe the entire physical world, from the smallest particles to the largest structure of the cosmos.

Often, string theory has been accused of merely providing abstract mathematical results and making too few predictions that can actually be verified in an experiment. Now, however, the string theory community all around the world is discussing a question that is closely related to cosmic experiments measuring the expansion of the universe. In 2011, the Nobel Prize in Physics was awarded for the discovery that the universe is not only constantly growing larger, but that this expansion is actually accelerating.

This phenomenon can only be explained by assuming an additional, previously unknown “dark energy.” This idea originally came from Albert Einstein, who added it as a “cosmological constant” to his theory of general relativity. Einstein actually did this to construct a non-expanding universe. When Hubble discovered in 1929 that the universe was in fact expanding, Einstein described this modification of his equations as the biggest blunder of his life. But with the discovery of the accelerated expansion of the cosmos, the cosmological constant has been reintroduced as dark energy into the current standard model of cosmology.

“This controversy is a good thing for string theory,” Timm Wrase is convinced. “Suddenly, a lot of people have completely new ideas which nobody has thought about before.” Wrase and his team are now investigating which fields are allowed in string theory and at which points they violate Vafa’s conjecture. “Maybe that leads us to exciting new insights into the nature of dark energy — that would be a great success,” says Wrase.

The hypotheses that arise will (at least in part) soon be tested experimentally. In the next few years the accelerated expansion of the universe will be measured more accurately than ever before. Paper.(open access) – Frederik Denef, Arthur Hebecker, Timm Wrase. de Sitter swampland conjecture and the Higgs potential. Physical Review D, 2018; 98 (8) DOI: 10.1103/PhysRevD.98.086004 More.

But could they accept, as a result of the upcoming test, an answer that did not include string theory, cosmic inflation, the multiverse, etc? Maybe we will get to see.